Laser welding of square butt joints between copper substrates

ABSTRACT

A method of joining electrical connections together includes evaluating at least one weld joint between at least two substrates, determining a mismatch between the at least two substrates, and welding the at least two substrates together with a multi-step welding process. The multi-step welding process includes compensating for the mismatch between the at least two substrates by welding on both sides but not overlapping a joint line between the at least two substrate with a first welding step and increasing melt volume and penetration depth of a weld between the at least two substrates with a second welding step.

FIELD

The present disclosure relates to welding and particularly laser weldingof hairpin wires and connectors of electric motor stators.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

High performance electric motors have increased conductor packingdensity and a uniform distribution of copper windings to reduce lossduring operation, improve NVH, and improve packaging space compared totraditional random wound, round wire windings. Also, uniformlydistributed rectangular windings are used to form stator windings withsuch an increase in conductor packing density.

Rectangular windings can be formed from individual wire segments thatare joined together to create a continuous electrical path. For example,spooled copper wire coated with a protective polymer layer isstraightened, cut into segments, and the segments bent into U-shapedsections often referred to as ‘hairpin’ sections or hairpin wires. Thehairpins are de-coated at joining locations (e.g., ends of the hairpins)prior to being fed through slots in a steel stator core and then joinedtogether to form the continuous electrical path, i.e., the statorwinding. In addition, connectors such as neutral connectors, terminalconnectors, and/or jumper connectors are included and joined to hairpinwires such that a desired stator winding is provided.

The present disclosure addresses issues related to joining hairpin wiresand connectors and other issues related to the manufacture of electricmotor stators.

SUMMARY

This section provides a general summary of the disclosure and is not acomprehensive disclosure of its full scope or all of its features.

In one form of the present disclosure, a method of joining electricalconnections together includes evaluating at least one weld joint betweenat least two substrates, determining a mismatch between the at least twosubstrates, and welding the at least two substrates together with amulti-step welding process. The multi-step welding process includescompensating for the mismatch between the at least two substrates bywelding on both sides but not overlapping a joint line between the atleast two substrate with a first welding step and increasing melt volumeand penetration depth of a weld between the at least two substrates witha second welding step.

In some variations, evaluating the at least one weld joint includesidentifying edges and center points of the at least two substrates,angular alignment of the at least two substrates relative to each other,gaps between the at least two substrates, and a vertical offset betweenthe at least two offset conditions.

In at least one variation, the first welding step includes weldinglinear weld segments biased towards but not overlapping the joint linebetween the at least two substrates and the second welding step includesoscillatory welding along the joint line between the at least twosubstrates.

In some variations, the at least two substrates comprise a wire and aconnector, for example, a hairpin wire and a connector. In at least onevariation, the at least two substrates include an end of a hairpin wireand a connector. And in some variations, the at least two substratescomprise a plurality of hairpin wire and connector pairs and welding theat least two substrates together comprises the plurality of weldinghairpin wire and connector pairs together by executing the first weldingstep and the second welding step on each of the plurality of hairpinwire and connector pairs. In at least one variation, the method furtherincludes assembling an electric motor stator via welding the pluralityof welding hairpin wire and connector pairs together. In somevariations, the plurality of hairpin and connector pairs are laserwelded together with a weld travel speed between 50 mm/s and 300 mm/s.

In at least one variation, the at least two substrates are verticallymisaligned from each other and the first welding step reduces thevertical mismatch before the second welding step.

In some variations, the at least one weld joint between the at least twosubstrates is evaluated with an electronic vision system. In suchvariations, the electronic vision system identifies at least oneposition of each the at least two substrates, a size of each the atleast two substrates, one or more edges of each the at least twosubstrates, a gap between the at least two substrates, an angle betweenthe at least two substrates, and/or a vertical offset between the atleast two substrates. In at least one variation the electronic visionsystem is co-axial to a laser beam welding the at least two substratestogether. And in some variations the electronic vision system is atleast one of a digital camera, a scanning optical coherence tomographysystem, a laser scanning system, and combinations thereof.

In some variations, the weld has a cross-sectional area equal to orgreater than an original cross-sectional area of the substrate. And inat least one variation the substrate has a cross-sectional area of 5square millimeters (mm²) and the weld has a cross-sectional area of atleast 5 mm².

In another form of the present disclosure, a method of joiningelectrical wiring together includes evaluating a weld joint between ahairpin wire and a connector, determining mismatch between the hairpinwire and the connector, welding at least two weld segments biasedtowards but not overlapping a joint line between the hairpin wire andthe connector during a first welding step, and oscillatory welding alongthe joint line between the hairpin wire and the connector during asecond welding step.

In some variations, the weld joint is evaluated with an electronicvision system prior to welding and the pre-weld evaluation includesidentifying edges and center points of the hairpin wire and theconnector, an angular alignment of the hairpin wire and the connectorrelative to each other, one or more gaps between the hairpin wire andthe connector, and a vertical offset between the hairpin wire and theconnector.

In at least one variation, the method further includes assembling anelectric motor stator via welding the ends of a plurality of hairpinwires and a plurality of connectors together with the first welding stepand the second welding step.

In still another form of the present disclosure, a method of joiningelectric motor stator wiring includes evaluating weld joints betweenhair pin segment-connector pairs of a stator winding with an electronicvision system, determining mismatch between the hair pinsegment-connector pairs with the electronic vision system andtransmitting at least one mismatch parameter to a laser welding system,laser welding linear weld segments biased towards but not overlapping ajoint line between each of the hair pin segment and connector pairsduring a first weld step and forming a weld across the joint line as afunction of the at least one mismatch parameter, and oscillatory weldingalong the joint line between each of the hair pin segment and theconnector pairs during a second weld step. In some variations, themethod further includes assembling an electric motor stator via weldingthe hairpin segment and connector pairs together with the first weldingstep and the second welding step.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a perspective view of a portion of an electric motor statorwith hairpin wires and connectors to form a stator winding of anelectric motor;

FIG. 2A is a perspective view of a hairpin wire-connector pair accordingto one variation of the present disclosure;

FIG. 2B is a perspective view of a hairpin wire-connector pair accordingto another variation of the present disclosure;

FIG. 2C is a perspective view of a hairpin wire-connector pair accordingto still another variation of the present disclosure;

FIG. 2D is a perspective view of a hairpin wire-connector pair accordingto yet another variation of the present disclosure;

FIG. 3A is a perspective view of one type of mismatch between a hairpinwire and a connector;

FIG. 3B is a perspective view of another type of mismatch between ahairpin wire and a connector;

FIG. 3C is a perspective view of still another type of mismatch betweena hairpin wire and a connector;

FIG. 3D is a perspective view of yet another type of mismatch between ahairpin wire and a connector;

FIG. 3E is a perspective view of still yet another type of mismatchbetween a hairpin wire and a connector;

FIG. 3F is a perspective view of another type of mismatch between ahairpin wire and a connector;

FIG. 3G is a top view of still another type of mismatch between ahairpin wire and a connector;

FIG. 4 is a side view of an assembly line with a laser welding systemaccording to the teachings of the present disclosure;

FIG. 5A is a top view of a hairpin wire-connector pair being joinedtogether with a first welding step according to one variation of thepresent disclosure;

FIG. 5B is a side view of a weld formed by the first welding step inFIG. 5A;

FIG. 5C is a top view of a hairpin wire-connector pair being joinedtogether with a first welding step according to another variation of thepresent disclosure;

FIG. 5D is a top view of a hairpin wire-connector pair being joinedtogether with a first welding step according to still another variationof the present disclosure;

FIG. 5E is a top view of a hairpin wire-connector pair being joinedtogether with a first welding step according to yet variation of thepresent disclosure;

FIG. 6A is a top view of the hairpin wire-connector pair in FIG. 5Ebeing welded during a second welding step according to the teachings ofthe present disclosure;

FIG. 6B is a side view of a weld formed by the second welding step inFIG. 6A; and

FIG. 7 is a flow chart for a method according to the teachings of thepresent disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIG. 1, a perspective view of a portion of an electricmotor stator 10 (referred to herein simply as “stator 10”) is shown. Thestator 10 includes a stator winding 100 and a stator core 170. In somevariations, the stator winding 100 is made out of copper or copper alloywire and the stator core 170 is made from a metal or alloy such assteel. The stator winding 100 is formed from a plurality of hairpin wiresections 110 (referred to herein simply as “hairpin wires” or “wires”)electrically connected (e.g., welded) to each other and electricallyconnected to connectors 120. Each of the hairpin wires 110 is bent orformed in a desired shape after insertion into and through the statorcore 170 and have a protective enamel coating ‘EC’ (e.g., a multi-layerPI, polyester, PAI or PEEK coating) to electrically insulate the hairpinwires 110 from the stator core 170. Also, the hairpin wires 110 are bentand arranged such that hairpin wire pairs 114 or hairpin wire-connectorpairs 130 can be joined (e.g., welded) together to form a desired statorwinding and stator for an electric motor. While the hairpin wires 110shown in FIG. 1 are rectangular hairpin wires 110 (i.e., have arectangular cross-section, e.g., in the x-y plane in FIG. 1), it shouldbe understood that hairpin wires with other cross-sectional shapes areincluded within the scope of the present disclosure.

Joining of the hairpin wire pairs 114 and the hairpin wire-connectorpairs 130 according to the teachings of the present disclosure does notproduce excessive damage to the protective enamel coating EC, producespatter or stray copper debris, or create a non-uniform shape whichcontacts another electrical connection or provide a place forelectricity to arc between isolated windings. It should also beunderstood that each hairpin wire pair 114 and each hairpinwire-connector pair 130 joined according to the teachings of the presentdisclosure have connections (i.e., welds) with low electricalresistivity, desired static strength, resistance to fatigue stresses(both vibrational and thermal) and consistent, low discontinuitymetallurgical properties.

Accordingly, and given that electrical connections are typically neededfor over 150 adjacent hairpin wire pairs 114 and hairpin wire-connectorpairs 130 for each stator 10, welding of the adjacent hairpin wire pairs114 and the hairpin-connector pairs 130 in a timely and cost efficientmanner is a complex manufacturing challenge.

Referring to FIGS. 2A-2D, examples of hairpin wire-connector pairs 130a-130 d and weld joints 140 a-140 d between hairpin wires 110 andconnectors 120 a-120 d are shown. For example, FIG. 2A shows a hairpinwire-connector pair 130 a with a hairpin wire 110 and a connector 120 a,and a weld joint 140 a with a single joint line 141 a between thehairpin wire 110 and the connector 120 a. Also, the weld joint 140 a isa simple butt weld joint with a single joint line 141 a between thehairpin wire 110 and the connector 120 a. While the joint line 141 a isshown as a linear joint line in FIG. 2A, in some variations the jointline 141 a can be non-linear. It should also be understood that a weldelectrically connecting the hairpin wire 110 to the connector 120 a isgenerally formed along the joint line 141 a and other joint linesdiscussed herein.

Referring to FIG. 2B, a hairpin wire-connector pair 130 b with a weldjoint 140 b having a first joint line 141 b and a second joint line 142b between the hairpin wire 110 and the connector 120 b is shown. Theconnector 120 b has a corner section (not labeled) for placement orpositioning of the hairpin wire 110 such that two sides 110 a, 110 b ofthe hairpin wire 110 can be welded to the connector 120 b.

FIG. 2C shows a hairpin wire-connector pair 130 c with a weld joint 140c having a first joint line 141 c, a second joint line 142 c, and athird joint line 143 c between with the hairpin wire 110 and theconnector 120 c. The connector 120 c has a slot section (not labeled)for placement or positioning of the hairpin wire 110 such that threesides 110 a, 110 b, 110 c of the hairpin wire 110 can be welded to theconnector 120 b.

FIG. 2D shows a hairpin wire-connector pair 130 d with two hairpin wires110 placed or positioned within a slot (not labeled) of a connector 120d. The hairpin wire-connector pair 130 d has a weld joint 140 d with afirst joint line 141 d, a second joint line 142 d, and a third jointline 143 d similar to the weld joint 140 c shown in FIG. 2C. However,the weld joint 140 d also includes a fourth joint line 144 d between thetwo hairpin wires 110. As shown in FIGS. 2A-2D, different types and/orconfigurations of weld joints are included in the manufacture of thestator 10.

Referring now to FIGS. 3A-3G, in some variations of the presentdisclosure a hairpin wire-connector pair 130 has a mismatch between thehairpin wire 110 and the connector 120. As used herein, the term“mismatch” refers to a physical, geometrical or chemical differencebetween a joining surface or edge of a hairpin wire 110 and a joiningsurface or edge of a connector 130 forming a hairpin wire-connector pair130. For example, FIG. 3A shows a hairpin wire-connector pair 130 c witha physical mismatch resulting from a difference in reflectivity betweenthe upper surface (+z direction) of the hairpin wire 110 and theconnector 120 c, and FIG. 3B shows a geometric mismatch resulting froman uneven upper surface of the hairpin wire 110. Also, FIG. 3C shows achemical mismatch resulting from a coating 127 (e.g., a thin metalliccoating) on the connector 120 c, FIG. 3D shows a geometric mismatchresulting from a vertical difference ‘Δz’ between an upper surface 110 dof the hairpin wire 110 and an upper surface 121 of the connector 120 c,and FIG. 3E shows a geometric mismatch resulting from a lateral gap ‘Δy’between an edge 112 of the hairpin wire 110 and an edge 122 of theconnector 120 c. FIG. 3F shows another geometric mismatch resulting froman insertion gap ‘Δx’ between another edge 112 of the hairpin wire 110and another edge 122 of the connector 120 c, and FIG. 3G shows stillanother geometric mismatch resulting from an angular misalignment ‘Δθ’between the hairpin wire 110 and the connector 120 c as measured by anangle between an edge 112 of the hairpin wire 110 and an edge 122 of theconnector 120 c. Accordingly, different types mismatches can be presentbetween a hairpin wire 110 and a connector 120 that a form a givenhairpin wire-connector pair 130.

Given the various types of weld joints and the range of mismatches thatcan be present between a hairpin wire 110 and a connector 120, it shouldbe understood that welding of hairpin wire-connector pairs 130 in a costand time efficient manner is a complex manufacturing process.Accordingly, and with reference to FIG. 4, a laser welding system 22 fortaking into account the various types of weld joints and compensatingfor the range of mismatches noted above is shown. In some variations, anassembly line 20 includes a conveyor ‘C’ that transports stators 10 witha plurality of hairpin wire-connector pairs 130 (not yet weldedtogether) through a laser welding station ‘S’ where the laser weldingsystem 22 is located.

The laser welding system 22 includes a laser source 210 with a fiber 212and an electronic vision system 220. One non-limiting example of thelaser source 210 is a 6 kW Trumpf TruDisk laser (1035 nm) with a TrumpfPFO-33 optic and one non-limiting example of the core ring fiber 212 isa Trumpf Brightline 50/200 um core ring fiber. Non-limiting examples ofthe electronic vision system 220 include a digital camera, a scanningoptical coherence tomography system, and a laser scanning system. Insome variations the electronic vision system 220 includes a controller222 for analysis of acquired images. In the alternative, or in additionto, the electronic vision system 220 uses an external controller (notshown) for analysis of acquired images.

The laser welding system 22 welds hairpin wire pairs 114 and hairpinwire-connector pairs 130 together to form a stator 10 a with acontinuous electrical path through the stator winding 100. In somevariations of the present disclosure, the laser welding system 22executes specific weld path shapes implemented by a multi-step weldingprocess. For example, in some variations the multi-step process is atwo-step process, while in other variations the multi-step processincludes more than two steps. And the laser welding system 22 isdirected by the electronic vision system 220 to create a robust jointbetween two or more substrates (e.g., a copper hairpin wire and a copperconnector) while inhibiting spatter generation and heat damage, as wellas mitigating manufacturing noise sources as described below.

Referring to FIGS. 5A-5B, a pre-weld evaluation and a first welding stepto join a hairpin wire 110 to a connector 120 c is shown in FIG. 5A anda first weld 215 resulting from the first welding step is shown in FIG.5B. During the pre-weld evaluation the electronic vision system 220acquires an image of the weld joint 140 c and/or the hairpinwire-connector pair 130 c shown in FIG. 5A. And the controller 222analyzes the image and determines edges 112 of the hairpin wire 110,edges 122 of the connector 120 c, a center point 113 of each edge 112, acenter point 123 of each edge 122, and any mismatch between the hairpinwire 110 and the connector 120 c. Stated differently, prior to welding ahairpin wire-connector pair 130 c, the electronic vision system 220 andthe controller 222 identify the location, size, part-to-part placementof the hairpin wire 110 relative to the connector 120 c, and anymismatch between the hairpin wire 110 relative to the connector 120 c.

After the image of the weld joint 140 c is analyzed, the controller 222determines (e.g., calculates) a weld path, a weld joint length, at leastone mismatch parameter, and/or one or more weld section origin point(s)(collectively referred to herein as “weld input parameters”) of the weldjoint 140 c. It should be understood that the weld path can includewhich edges 112, 122 of a hairpin wire-connector pair 130 are to bewelded together. In some variations the weld path includes welding asingle pair of edges 112, 122 together, while in other variations theweld path includes welding two pair of edges 112, 122 together (FIGS.5C-5D), and in at least one variation the weld path includes weldingthree pair of edges 112, 122 together (FIG. 5E). Also, non-limitingexamples of the at least one mismatch parameter include a reflectivelydifference value between an upper surface of the hairpin wire 110 upperand an upper surface of the connector 120 c, a metallic coatingdetection value, at least one geometric Δx, Δy, and/or Δz value, and ageometric Δθ value, among others.

The weld input parameters are transmitted to the laser welding system22, and in response thereto, the laser welding system 22 directs thecore ring fiber 212 (and a laser beam B) along a laser patterncomprising multiple shaped laser weld segments. For example, and basedon the weld input parameters, the laser welding system 22 executes afirst welding step that includes welding on both sides (+x direction and−x direction) of, but not overlapping, a joint line 213 of the weldjoint 140 c. In at least one variation of the present disclosure, thelaser welding system 22 executes a first weld segment 214 a on one side(+x direction) of, but not overlapping, the joint line 213 and a secondweld segment 214 b on an opposite side (−x direction) of, but notoverlapping, the joint line 213. In some variations, the first weldsegment 214 a and the second weld segment 214 b are biased towards, butdo not overlap, the joint line 213 between the hairpin wire 110 and theconnector 120 c. It should be understood that the dashed ellipses inFIG. 5A represent an edge of a laser beam B (FIG. 4) propagating fromthe core ring fiber 212 to the hairpin wire 110 and the connector 120 c,and the solid arrows 214 a, 214 b represent a path traversed by a centerof the laser beam B.

In some variations, the laser welding system 22 executes a single pass(i.e., a single laser beam pass) to form the first weld segment 214 aand/or the second weld segment 214 b, while in other variations thelaser welding system 22 executes more than one pass (e.g., rapidrepetition) to form the first weld segment 214 a and/or the second weldsegment 214 b. That is, depending on the type and degree (magnitude) ofmismatch between the hairpin wire 110 and the connector 120 c, multiplelaser beam passes can be executed to reduce the degree of mismatch. Inaddition, a length ‘A1’ of the first weld segment 214 a, a length ‘A2’of the second weld segment 214 b, and lengths of other weld segmentsdiscussed herein, can be predefined for a given type of hairpinwire-connector and/or determined as a function of the weld inputparameters, process parameters, and equipment tolerances, size of agiven/particular hairpin wire being welded, among others.

Although the first weld segment 214 a and the second weld segment 214 bare biased towards, but do not overlap, the joint line 213 between thehairpin wire 110 and the connector 120 c, in some variations of thepresent disclosure molten material from one or both sides of the jointline 213 (i.e., from the hairpin wire 110 and/or the connector 120 c)overlaps the joint line 213 and forms a first weld 215 as shown in FIG.5B. That is, it should be understood that a weld segment can have amolten pool that is larger than the diameter of the laser beam formingthe weld segment. Accordingly, the first welding step forms a weldacross the weld joint 140 c without the laser beam B propagating betweenthe hairpin wire 110 and the connector 120 c.

It should be understood that forming the weld 215 using the firstwelding step reduces thermal damage to the enamel coating EC (FIG. 1),weld spatter and/or weld contamination. In addition, the first weldingstep creates a smooth uniform surface to be welded on during a secondwelding step described below, but does not generate significant weldvolume. It should also be understood that the melt generated by thelinear segments 214 a, 214 b removes or reduces variation due toinconsistent surface reflectivity, surface profile, or surfacecontamination and melts or removes thin coatings (e.g. tin) that may bepresent on the connector 120 c.

While FIG. 5A shows an example of a weld along a single pair of edges112, 122 (i.e., one side) between the hairpin wire 110 and the connector120 c, examples of welds along two pairs of edges (i.e., two sides) areshown in FIGS. 5C-5D and an example of a weld along three pairs of edges(i.e., three sides) is shown in FIG. 5E. Particularly, and referring toFIG. 5C, the hairpin wire 110 is laterally offset within the slot (notlabeled) of the connector 120 c towards an upper (+y direction) edge 122such that a lateral gap Δy is present between a lower (−y direction)edge 112 of the hairpin wire 110 and a lower edge 122 of the connector120 c. The electronic vision system 220 detects and analyzes thegeometric mismatch between the hairpin wire-connector pair 130 c shownin FIG. 5C and determines the weld input parameters. Also, the laserwelding system 22 executes a first weld segment 214 a along two edges112 of the hairpin wire 110 and a second weld segment 214 b alongopposing edges 122 of the connector 120 c as shown in FIG. 5C and as afunction of the weld input parameters. That is, the laser welding system22 executes the first weld segment 214 a on one side (+x direction) ofthe joint line 213 and the second weld segment 214 b on an opposite side(−x direction) of the joint line 213 such that the first and second weldsegments 214 a, 214 b are biased towards, but do not overlap, the jointline 213 between the hairpin wire 110 and the connector 120 c. In somevariations, the laser welding system 22 executes a single pass (i.e., asingle laser beam pass) to form the first weld segment 214 a and/or thesecond weld segment 214 b, while in other variations the laser weldingsystem 22 executes more than one pass (e.g., rapid repetition) to formthe first weld segment 214 a and/or the second weld segment 214 b.

Referring to FIG. 5D, the hairpin wire 110 is laterally positioned inthe slot (not labeled) of the connector 120 c such that lateral gaps Δy1and Δy2 are present between the upper and lower edges 112 (FIG. 5C) ofthe hairpin wire 110 and corresponding upper and lower edges 122 (FIG.5C) of the connector 120 c. Also, the hairpin wire 110 is positioned inthe slot of the connector 120 c such that an insertion gap Δx is presentbetween the edge 112 of the hairpin wire 110 and the edge 122 of theconnector 120 c as shown in FIG. 5D. Accordingly, the electronic visionsystem 220 detects and analyzes the mismatch between the hairpinwire-connector pair 130 c shown in FIG. 5D and determines the weld inputparameters. Then, the laser welding system 22 executes a first weldsegment 214 a along the two edges 112 of the hairpin wire 110 and asecond weld segment along the opposing two edges 122 of the connector120 c shown in FIG. 5D, and as a function of the weld input parameters.That is, the laser welding system 22 executes the first weld segment 214a on a hairpin wire side of the joint line 213 and the second weldsegment 214 b on a connector side of the joint line 213 such that thefirst and second weld segments 214 a, 214 b are biased towards, but donot overlap, the joint line 213 between the hairpin wire 110 and theconnector 120 c. In some variations, the laser welding system 22executes a single pass (i.e., a single laser beam pass) to form thefirst weld segment 214 a and/or the second weld segment 214 b, while inother variations the laser welding system 22 executes more than one pass(e.g., rapid repetition) to form the first weld segment 214 a and/or thesecond weld segment 214 b.

Referring to FIG. 5E, the hairpin wire 110 is laterally positioned inthe slot (not labeled) of the connector 120 c such that lateral gaps Δy1and Δy2 are present between the upper and lower edges 112 (FIG. 5C) ofthe hairpin wire 110 and corresponding upper and lower edges 122 (FIG.5C) of the connector 120 c. Also, the hairpin wire 110 is positioned inthe slot of the connector 120 c such that an insertion gap Δx is presentbetween the edge 112 of the hairpin wire 110 and the edge 122 of theconnector 120 c shown in FIG. 5E. Accordingly, the electronic visionsystem 220 detects and analyzes the mismatch between the hairpinwire-connector pair 130 c shown in FIG. 5E and determines the weld inputparameters. Then, the laser welding system 22 executes a first weldsegment 214 a along the three edges 112 of the hairpin wire 110 and asecond weld segment 214 b along the three opposing edges 122 of theconnector 120 c as shown in FIG. 5E as a function of the weld inputparameters. That is, the laser welding system 22 executes the first weldsegment 214 a on the hairpin wire side of the joint line 213 and thesecond weld segment 214 b on the connector side of the joint line 213such that the first and second weld segments 214 a, 214 b are biasedtowards, but do not overlap, the joint line 213 between the hairpin wire110 and the connector 120 c. In some variations, the laser weldingsystem 22 executes a single pass (i.e., a single laser beam pass) toform the first weld segment 214 a and/or the second weld segment 214 b,while in other variations the laser welding system 22 executes more thanone pass (e.g., rapid repetition) to form the first weld segment 214 aand/or the second weld segment 214 b.

It should be understood that in some variations of the presentdisclosure that the first weld segment 214 a is a continuous weldsegment and/or the second weld segment 214 b is a continuous weldsegment. It should also be understood that in some variations the firstweld segment 214 a and the second weld segment 214 b described abovewith respect to FIGS. 5C-5E form a first weld 215 across the joint line213 as described above and shown in FIG. 5B.

Referring now to FIGS. 6A-6B, the laser welding system 22 executes asecond welding step over the joint line 213 shown in FIG. 5E such thatan increase in melt volume and penetration depth of the first weld 215results in a final weld 217 between the hairpin wire 110 and theconnector 120 c. Particularly, the laser welding system 22 executes asecond weld 216 over the joint line 213, and in at least one variationthe laser welding system 22 executes at least one continuous oscillatoryweld 216 over the joint line 213 as depicted in FIG. 6A. In somevariations, the energy input, welding speed, and/or number ofoscillatory patterns are a function of the at least one mismatchparameter determined by the electronic vision system 220.

In some variations the segment lengths ‘A’, ‘B’, and ‘C’ shown in FIG.5E and/or FIG. 6A is a function of a measured hairpin wire dimension(WD), laser beam diameter (BD), and a vision tolerance (VT) of theelectronic vision system 220. For example, and assuming the hairpin wire110 has a y-direction dimension of 3 millimeters (mm), an x-directiondimension of 2 mm, the diameter of the laser beam B is 680 micrometers(μm), and the vision tolerance of the electronic vision system 220 is 50μm, a segment length B was calculated as WD−BD−2VT=3 mm-680 um-100um=2.22 mm. In addition, for an original cross-sectional area (x-yplane) of the hairpin wire 110 being a 6 mm² and a desired 6 mm² weldcross-sectional area between the hairpin wire 110 and the connector 120c, the hairpin wire 110 was welded on three sides with a forward travelspeed of 130 mm/s. And for the same hairpin wire 110 welded on two sides(i.e., with one side unwelded), a forward travel speed of 70 mm/s wasused to create a deeper and larger weld in order to maintain at least 6mm² cross-sectional area between the hairpin wire 110 and the connector120 c. Also, the power level of the laser beam B was reduced and/ortravel speed increased near an end of a weld trace to reduce the impactof melt down near edges and at a crater location. It should beunderstood that a weld cross-sectional area is measured along one ormore planes between a hairpin wire and a connector. For example, in FIG.6A, the weld cross-sectional area is measured along the y-z plane andthe two x-z planes between the hairpin wire 110 and the connector 120 c.

It should be understood that using a continuous oscillatory laser beampass tracing the joint line 213 results in maintaining keyhole stabilitywhile enhancing outgassing of absorbed gasses, voids or porosity fromthe molten pool. And a rapid growth phase of the weld reduces the amountof cycle time as compared to the cycle time needed for the same weldvolume using only linear segments. Due to the instability of weldingcopper with an IR-wavelength laser, the oscillatory shape of the pathallows for achieving adequate beam speed, maintaining stability in deeppenetration welding, and rapid growth of the weld pool minimizes totalheat input and resultant thermal impact to the hairpin wire 110 andconnector 120 c.

Referring now to FIG. 7, a method 30 of joining electrical connectionstogether is shown. The method 30 includes evaluating a weld jointbetween two substrate at 300, determining any mismatch between the twosubstrates at 310, and welding first weld segments biased towards butnot overlapping a joint line between the two substrates with a firstwelding step at 320. The method also includes welding a second weldsegment over the joint line between the two substrates with a secondwelding step at 330. In this manner, a continuous electrical paththrough the stator winding 100 is provided with each hairpinwire-connector pair 114 connected with a weld that has low electricalresistivity, desired static strength, resistance to fatigue stresses(both vibrational and thermal) and consistent, low discontinuitymetallurgical properties.

In view of the teachings of the present disclosure, it should beunderstood that a laser welding system and method of welding substratestogether is provided. Also, the laser welding system and the methodnormalizes surface conditions of wires and or connectors, adapts tomisalignment conditions caused by lateral gaps, insertion gaps, andvertical offsets, adapts to varied wire size, dimension, and location,and prevents enamel and tooling damage from laser light passing throughthe joint line during the welding process. In addition, the laserwelding system and the method provides a balanced heat input to allcomponents while maintaining low cycle times and preventing spattergeneration while achieving a robust mechanical and electricalconnection.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove or below.

Unless otherwise expressly indicated herein, all numerical valuesindicating mechanical/thermal properties, compositional percentages,dimensions and/or tolerances, or other characteristics are to beunderstood as modified by the word “about” or “approximately” indescribing the scope of the present disclosure. This modification isdesired for various reasons including industrial practice, material,manufacturing, and assembly tolerances, and testing capability.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.”

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A method of joining electrical connectionstogether, the method comprising: evaluating at least one weld jointbetween at least two substrates; determining a mismatch between the atleast two substrates; and welding the at least two substrates togetherwith a multi-step welding process comprising compensating for themismatch between the at least two substrates by welding on both sidesbut not overlapping a joint line between the at least two substrate witha first welding step and increasing melt volume and penetration depth ofa weld between the at least two substrates with a second welding step.2. The method according to claim 1, wherein evaluating the at least oneweld joint comprises identifying edges and center points of the at leasttwo substrates, angular alignment of the at least two substratesrelative to each other, gaps between the at least two substrates, and avertical offset between the at least two offset conditions.
 3. Themethod according to claim 1, wherein the first welding step compriseswelding linear weld segments biased towards but not overlapping thejoint line between the at least two substrates and the second weldingstep comprises oscillatory welding along the joint line between the atleast two substrates.
 4. The method according to claim 1, wherein the atleast two substrates comprise a wire and a connector.
 5. The methodaccording to claim 1, wherein the at least two substrates comprise ahairpin wire and a connector.
 6. The method according to claim 1,wherein the at least two substrates comprise an end of a hairpin wireand a connector.
 7. The method according to claim 6, wherein the atleast two substrates comprise a plurality of hairpin wire-connectorpairs and welding the at least two substrates together comprises weldingthe plurality of welding hairpin wire-connector pairs together byexecuting the first welding step and the second welding step on each ofthe plurality of hairpin wire-connector pairs.
 8. The method accordingto claim 7 further comprising assembling an electric motor stator viawelding the plurality of welding hairpin wire-connector pairs together.9. The method according to claim 8, wherein the plurality of hairpin andconnector pairs are laser welded together with a weld travel speedbetween 50 mm/s and 300 mm/s.
 10. The method according to claim 1,wherein the at least two substrates are vertically misaligned from eachother and the first welding step reduces the vertical misalignmentbefore the second welding step.
 11. The method according to claim 1,wherein the at least one weld joint between the at least two substratesis evaluated with an electronic vision system.
 12. The method accordingto claim 11, wherein the electronic vision system identifies at leastone of a position of each the at least two substrates, a size of eachthe at least two substrates, one or more edges of each the at least twosubstrates, a gap between the at least two substrates, an angle betweenthe at least two substrates, and a vertical offset between the at leasttwo substrates.
 13. The method according to claim 12, wherein theelectronic vision system is co-axial to a laser beam welding the atleast two substrates together.
 14. The method according to claim 13,wherein the electronic vision system is at least one of a digitalcamera, a scanning optical coherence tomography system, a laser scanningsystem, and combinations thereof.
 15. The method according to 14,wherein the weld has a cross-sectional area between the at least twosubstrates equal to or greater than an original cross-sectional area ofat least one of the at least two substrates.
 16. A method of joiningelectrical wiring together, the method comprising: evaluating a weldjoint between a hairpin wire and a connector; determining mismatchbetween the hairpin wire and the connector; welding at least two weldsegments biased towards but not overlapping a joint line between thehairpin wire and the connector during a first welding step; andoscillatory welding along the joint line between the hairpin wire andthe connector during a second welding step.
 17. The method according toclaim 16, wherein the weld joint is evaluated with an electronic visionsystem and the evaluating comprises identifying edges and center pointsof the hairpin wire and the connector, an angular alignment of thehairpin wire and the connector relative to each other, one or more gapsbetween the hairpin wire and the connector, and a vertical offsetbetween the hairpin wire and the connector.
 18. The method according toclaim 17 further comprising assembling an electric motor stator viawelding the ends of a plurality of hairpin wires and a plurality ofconnectors together with the first welding step and the second weldingstep.
 19. A method of joining electric motor stator wiring, the methodcomprising: evaluating weld joints between hairpin wire-connector pairsof a stator winding with an electronic vision system; determiningmismatch between the hairpin wire-connector pairs with the electronicvision system and transmitting at least one mismatch parameter to alaser welding system; laser welding linear weld segments biased towardsbut not overlapping a joint line between each of the hairpinwire-connector pairs during a first weld step and forming a weld acrossthe joint line as a function of the at least one mismatch parameter; andoscillatory welding along the joint line between each of the hairpinwire-connector pairs during a second weld step.
 20. The method accordingto claim 19 further comprising assembling an electric motor stator viawelding the hairpin wire-connector pairs together with the first weldingstep and the second welding step